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Old 21st November 2009, 07:32 AM   #1
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Default Advice with modification of Beard power amp

Hi all,

I have a Beard P100 power amp and recently came upon a schematic that showed a modification to the feedback loop of the amplifier. The modification adds a 6.8K resistor and 330pf capacitor to the existing 5.6K resistor and 330pf capacitor in parallel. See attached schematic.



I am trying to understand what such a modification would do and what I should expect in terms of sound.

Thanks
Ronen
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Old 21st November 2009, 07:38 AM   #2
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decreased sensitivity , and tiny difference in sound , induced by increased feedback .

will you like it - it's probably matter of taste
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Old 21st November 2009, 09:34 AM   #3
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I used to have a P100 (the early black type with the handles). IIRC the usual (and best) modifications were self-bias (getting rid of that unreliable fixed-bias circuitry), and pseudo-triode mode for the 6550a's (always liked the GE6550a's best). And of course try a nice copper-foil coupling cap. Those mods were done before I got the amp, I bought it from someone who became a friend and who showed me that building your own gear is great fun.
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Old 21st November 2009, 01:12 PM   #4
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Thanks for the advise.

I actually already replaced all rectifier caps with new one (JJ 800uf bypassed with ClarityCap 0.1uf) and replaced all coupling capacitors to Auricap and ClarityCap SA series. this made a great difference and now puts the Beard equal to the Conrad Johnson Premier 12 I have.
I am not sure how I can achieve a self bias circuit and am not sure about its benefit as every tube amp I owned had a potentiometer based bias circuit similar to the Beard. Any ideas?

I was also thinking about changing the fillament supply to DC. Currently its AC in the Beard. This will require an external transformer and rectification citcuit as there is no room to place such a circuit inside the amp.

Any other mod suggestions? This is really a killer amp. I have had many amp over the years all came and gone and the Beard is still here after 15 years sounding better then ever.

Thanks
ronenash
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Old 21st November 2009, 01:14 PM   #5
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One more thing... Can anyoneguide me on how to modify the Beard for Triod mode?

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ronenash
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